Bead Size Converter
Seed bead aught to mm.
Seed bead aught to mm.
How to use Bead Size Converter
- Pick a seed bead size in the aught system
- Read the round and cylinder Delica millimetre sizes side by side
- Check how many beads fit per inch
About Bead Size Converter
Seed bead sizes use the old aught system, where a bead is written as a number over a zero — 11/0, read "eleven-aught." This chart converts each aught size to its actual size in millimetres, so you can see how big a bead really is instead of guessing from the number. Pick a size and it shows the round-bead millimetre range and the cylinder (Delica) millimetre range side by side, plus roughly how many beads fit per inch.
The aught system runs backwards — a bigger number means a smaller bead — which trips up almost everyone new to beading. The millimetre size also shifts by brand, so the tool gives a range rather than one exact figure and lets you compare Japanese beads (Miyuki, Toho) against Czech beads at the same aught. It also keeps round seed beads and Delica cylinders separate, because an 11/0 round and an 11/0 Delica are not the same size or shape even though they share a number.
Use it as a quick size comparison when you're substituting one brand for another, checking how many beads a pattern needs, or working out the real millimetre width before you buy. Since it's a plain web page, you can print it straight from your browser if you want a paper reference on your worktable. It's completely free with no sign-up, and it runs entirely in your browser — nothing is uploaded.
Frequently asked questions
- What size is an 11/0 seed bead in mm?
- About 1.8–2.2 mm across for a round seed bead, with roughly 18 beads per inch. Japanese 11/0 beads run a touch smaller and more uniform than Czech ones.
- Can I convert seed bead aught sizes to millimetres?
- Yes. Choose an aught size and the tool shows its millimetre range for round beads and for Delica cylinders. Because brands vary, it gives a range — an 11/0 round is roughly 1.8–2.2 mm — rather than one exact figure.
- How do I see the actual size of a seed bead?
- The chart lists the true millimetre width for each aught size, so you can hold a millimetre ruler against a bead and match it up — an 11/0 round runs about 1.8–2.2 mm, an 8/0 around 3 mm. That real measurement is more reliable than eyeballing the aught number, since actual size shifts by brand.
- How do I compare two seed bead sizes side by side?
- For any size you pick, the tool puts the round-bead and Delica cylinder millimetres side by side and lists an approximate beads-per-inch. To compare two aught sizes, look each one up — the millimetre ranges make it easy to see how much bigger, say, an 8/0 is than an 11/0.
- Why is a bigger aught number a smaller bead?
- The number is an old count of how many beads fit in a given length, so more beads means each one is smaller — a 15/0 is smaller than an 8/0. It's read '15-aught.'
- Is a Delica the same size as a round 11/0?
- No. Miyuki Delicas are cylinder beads, so an 11/0 Delica (about 1.6 mm) is a different size and shape from an 11/0 round seed bead, even though they share the aught number.
- Do Czech and Japanese seed beads differ in size?
- Yes — Japanese beads (Miyuki, Toho) are more uniform and usually a little smaller than Czech beads of the same aught, which is why the tool gives a range rather than one exact number.
- What is the Miyuki seed bead size chart?
- Miyuki is a Japanese maker, so its seed beads are more uniform and usually slightly smaller than Czech beads of the same aught. Select a size and you'll see the millimetre range that covers Japanese brands like Miyuki and Toho, alongside the Czech range for comparison.
- What sizes do Toho seed beads come in?
- Toho beads come in the same aught sizes as other brands — 15/0, 11/0, 8/0, 6/0 and so on — and, being Japanese, sit at the smaller, more uniform end of each millimetre range. The tool shows those Japanese ranges so you can match Toho against Miyuki or Czech beads.
- How many seed beads are there per inch?
- Roughly 18 for 11/0, 12 for 8/0 and 24 for 15/0 — the tool lists an approximate beads-per-inch for each size to help you estimate quantities.
- Can I print this seed bead size chart?
- Yes. It's an ordinary web page, so you can print it from your browser (Ctrl+P or Cmd+P) to keep a paper copy by your beadwork. Nothing needs to be downloaded or installed first.
- Are all seed beads glass?
- The common seed beads these sizes describe — Miyuki, Toho and Czech rounds, plus Delicas — are glass, which is why sizes stay fairly consistent within a brand. The aught sizing and millimetre ranges here apply to those standard glass seed beads.
- What needle size do I need for a seed bead?
- This chart covers bead sizes rather than needles, but as a rough guide a size 10 or 11 beading needle passes through most 11/0 beads, a size 12 or 13 suits tiny 15/0s, and a size 10 works for larger 8/0s. Match the needle to the smallest bead and the number of thread passes your pattern needs.